Various methods of direct exploration of body cavities are known for medical diagnosis and treatment. One example is the capsule endoscope, which has been used in the diagnosis of small intestine bleeding and detection of Crohn's Disease, Celiac disease, and other malabsorption disorders, as well as benign and malignant tumors of the small intestine. The capsule endoscope includes essentially a camera in a pill form that the subject swallows. As the capsule passes through the digestive tract of the subject, the camera captures many pictures of the tract. After the capsule passes out of the subject, the pictures are retrieved and analyzed. The capsule endoscope can reach areas of the small intestine that a conventional endoscope cannot.
Although capsule endoscopy is an improved technique for detecting sources of small bowel bleeding, it does not achieve 100% detection. The capsule is purely diagnostic and cannot be used to take biopsies, apply therapy, or mark abnormalities for surgery. Moreover, the capsule cannot be controlled once it has been ingested, so that its progress cannot be slowed to better visualize a suspicious abnormality.
Swimming capsules are an advanced version of capsule (also called a swimming micro-robot) that can be actively positioned by propulsion. One such device included piezoelectric actuators based on ionic conducting polymer film. A later similar device included a symmetrical structure with four fins that allowed the micro-robot to turn as well as swim. Changing the frequency of one of the two piezoelectric actuators enabled turning.
Another known approach includes a micro-robot powered by a static magnetic field. The swimming mechanism in this approach included a helix tail in an alternating magnet field generated by a physically rotating permanent magnet. The micro-robot was made of a spiral copper wire and a SmCo permanent magnet attached to its tip. By applying an external alternating magnetic field, magnetic torque can be created at the tip of the spiral copper wire. Alternatively, an electrically generated magnetic field could be used.
Yet another known approach includes using a magnetic actuator composed of a magnet and spiral structure that can be moved wirelessly by applying an external magnetic field. The magnetic actuator in this approach was composed of a capsule dummy, a permanent magnet inside the capsule, and a spiral structure. The actuator was rotated and propelled wirelessly by applying an external rotational magnetic field. The capsule, however, can only move forwards or backwards in the gastro-intestinal (“GI”) tract and depends on the assumption that the capsule always has contact with the GI tract. Thus, three-dimensional position and orientation control of the capsule is not possible, prohibiting the range of its application in GI tract.
Another disadvantage to previous approaches is that the location of the previous swimming micro-robots could not be determined during examination. Magnetic resonance imaging (“MRI”), a minimally invasive yet comprehensive imaging technology, may provide this capability; however, the above approaches used ferro-magnetic materials such as a permanent magnet in the capsule and rotating local magnetic fields to generate propulsion. Such propulsive mechanisms cannot be combined with MRI due to the interaction of the ferro-magnetic material with an MRI's magnetic field. It is also difficult to place an additional set of magnetic field generators inside an MRI device and also virtually any other medical imaging device.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.